Fornax Disaster

From Memory Alpha, the free Star Trek reference.

In an illusion created by Barash for William Riker, the Fornax Disaster took place sometime between 2367 and 2383. A star going nova threatened a colony, but the USS Enterprise-D, under Riker's command, arrived in time to save all the colonists.

Jean-Luc Riker, Will's imaginary son, claimed to have been asked about this incident in school by his teacher, Mr. Greenburg, but he did not to know the exact stardate. (TNG: "Future Imperfect")